European Aviation Safety Agency

ATA 67 – Rotors Flight Control – Tail Rotor Control Stop Screws – Inspection
 N AD 2011-0164R1

Annotation

Reason:

During take-off with a sling load, the pilot of an AS 350 B3 helicopter noticed that one of the yaw stops had been reached before its usual position. The subsequent inspection revealed that a nut of the tail rotor control stop was loose and that the corresponding tail rotor control stop screw was out of adjustment.

This condition, if not detected and corrected, can lead to the loss of adjustment of the affected stop and consequently limit yaw authority, possibly resulting in loss of control of the helicopter.

To address this potential unsafe condition, Eurocopter published Alert Service Bulletin (ASB) AS350-05.00.64 and ASB AS355-05.00.59, providing inspection instructions. Consequently, EASA issued AD 2011-0164 to require repetitive inspections of the tail rotor control stop screws and, depending on findings, adjustment.

Since that AD was issued, following further analysis and design activities performed by Airbus Helicopters (AH), it was determined that the inspection interval could be extended from 110 flight hours (FH) to 165 FH. AH also developed, for certain helicopters, a modification (mod 074602) that would delete the need for repetitive inspections.

For the reason described above, this AD is revised to extend the inspection interval, and to introduce an optional modification, valid only for post-mod 072295 helicopters, that constitutes terminating action for the repetitive inspections as required by this AD.

This AD also contains some editorial changes for standardization purposes, without affecting the requirements.